Dude completely understand that. I didn't start playing online seriously till halo reach. Used to play against friends split screen what not, thought I was pretty decent till I took it online. I remember being really frustrated for a long time just getting owned but I loved the game enough I wanted to get better so i stuck with it. It took me forever to get my kd in reach back to 1! But it got there. Same with sniping. Practice in PvE first for sure. Get a feel for the snipers you have and which ones you like to use as well as the scopes on em. That's big.